Notorious big G: The struggle to pin down gravity

Update:On 2 June 2011, Barry Wood's committee released its new recommended values for the fundamental physical constants. The value for "big G" was reduced by 66 parts per million, and the uncertainty on it increased from 100 parts per million to 120 parts per million.

Original article from 23 April 2011 issue:

We've been measuring gravity for 200 years, but we're still not sure how strong it is. Meet the metrologists striving to find out

HAROLD PARKS'S belongings were already leaving for France when he realised gravity had given him the slip. "The movers were in my apartment taking my stuff away," he says. He was in his lab at the research institute JILA in Boulder, Colorado, making the final checks on an experiment that had taken up the past two years of his life - to precisely measure the strength of gravity. "The signal ...

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